单选题 'Usually when we walk through the rain forest we hear a soft sound from all the moist leaves and organic debris on the forest floor, ' says ecologist Daniel Nepstad. 'Now we increasingly get rustle and crunch. That's the sound of a dying forest.'
Predictions of the collapse of the tropical rain forests have been around for years. Yet until recently the worst forecasts were almost exclusively linked to direct human activity, such as clear-cutting and burning for pastures or farms. Left alone, it was assumed, the world's rain forests would not only flourish but might even rescue us from disaster by absorbing the excess carbon dioxide and other planet-warming greenhouse gases. Now it turns out that may be wishful thinking. Some scientists believe that the rise in carbon levels means that the Amazon and other rain forests in Asia and Africa may go from being assets in the battle against rising temperatures to liabilities. Amazon plants, for instance, hold more than 100billion metric tons of carbon, equal to 15 years of tailpipe and chimney emissions. If the collapse of the rain forests speeds up dramatically, it could eventually release 3.5-5 billion metric tons of carbon into the atmosphere each year—making forests the leading source of greenhouse gases,
Uncommonly severe droughts brought on by global climate changes have led to forest-eating wildfires from Australia to Indonesia, but nowhere more acutely than in the Amazon. Some experts say that the rain forest is already at the brink of collapse.
Extreme weather and reckless development are plotting against the rain forest in ways that scientists have never seen. Trees need more water as temperatures rise, but the prolonged droughts have robbed them of moisture, making whole forests easily cleared of trees and turned into farmland. The picture worsens with each round of El Ni?o, the unusually warm currents in the Pacific Ocean that drive up temperatures and invariably presage (预示) droughts and fires in the rain forest. Runaway fires pour even more carbon into the air, which increases temperatures, starting the whole vicious cycle all over again.
More than paradise lost, a perishing rain forest could trigger a domino effect—sending winds and rains kilometers off course and loading the skies with even greater levels of greenhouse gases—that will be felt far beyond the Amazon basin. In a sense, we are already getting a glimpse of what's to come. Each burning season in the Amazon, fires deliberately set by frontier settlers and developers hurl up almost half a billion metric tons of carbon a year, placing Brazil among the top five contributors to greenhouse gases in the world.

单选题 We learn from the first paragraph that ______.

A、 dead leaves and tree debris make the same sound
B、 trees that are dying usually give out a soft moan
C、 organic debris echoes the sounds in a rain forest
D、 the sound of a forest signifies its health condition

【正确答案】 D

【答案解析】由题干中的the first paragraph直接定位到第一段。推理判断题。第一段引用了生态学家Daniel Nepstad的话，从中可知人们穿越热带雨林时，可以听到湿润的树叶和地上有机物碎屑发出的轻柔的声音，但是现在人们大多听到沙沙声和嘎吱嘎吱的声音，这是森林垂死挣扎的声音。也就是说，不同的声音代表了热带雨林不同的健康状况。轻柔声意味着热带雨林繁茂，而沙沙声和嘎吱嘎吱的声音则意味着热带雨林濒临瓦解，故答案为D。 [参考译文] “通常，当我们穿越热带雨林时，我们能听到所有湿润的树叶和地上有机物碎屑发出的轻柔的声音，”生态学家Daniel Nepstad说，“现在，我们越来越多地听到沙沙声和嘎吱嘎吱的声音。那是森林垂死挣扎的声音。” 关于热带雨林瓦解的预测已经有很多年了。然而，一直到最近，这种最糟糕的预测几乎都只和直接的人类活动联系在一起，如为了兴建牧场或农场而大肆砍伐和焚烧雨林。根据假设，如果任由热带雨林发展，世界上的热带雨林不仅会繁茂旺盛，而且通过吸收过多的二氧化碳和其他温室气体，热带雨林甚至可能拯救人类远离灾难。现在看来那可能只是一厢情愿的想法。有些科学家认为碳含量的上升表明，在对抗不断上升的气温的斗争中，亚马逊地区和其他亚非地区的热带雨林可能从财富转变为负债。举例来说，亚马逊的植被储存了1000多亿公吨碳，这相当于15年尾气和烟囱的排放量。如果热带雨林瓦解的速度显著加快，其最终每年向大气中释放35～50亿公吨的碳量——使森林成为温室气体的主要来源。由全球气候变化造成的非常严重的干旱导致了吞噬森林的野火，野火从澳大利亚蔓延至印度尼西亚，但是亚马逊地区最为严重。一些专家认为热带雨林已经濒临瓦解。极端天气和不计后果的开发以科学家从未见过的方式破坏着热带雨林。由于气温升高，树木需要更多的水，但是持久的干旱使它们丧失水分，这使得整个森林被很轻易地清理掉树木而变成农场。每一轮厄尔尼诺海流——太平洋上的异常暖流，其升温总能预示热带雨林的干旱和大火——都会使这种情况变得更加糟糕。失控的大火向空气中排放更多的碳，造成气温上升，从而使这个恶性循环再一次发生。这不仅仅是失去乐园，即将毁灭的热带雨林可能引发多米诺效应——使风和雨偏离方向数千米，向空中排放更多的温室气体——在远离亚马逊盆地的地方就能感受到。在某种意义上，我们已经窥察到将要发生的景象。在亚马逊的每个燃烧季节，拓荒者和开发者蓄意点燃的大火一年向空中排放将近5亿公吨的碳，使巴西成为导致温室气体的前五个因素之一。

单选题 In the second paragraph, the author challenges the view that _____ .

A、 the collapse of rain forests is caused by direct human interference
B、 carbon emissions are the leading cause of current global warming
C、 the condition of rain forests has been rapidly deteriorating
D、 rain forests should not be converted into pastures or farms

【正确答案】 A

【答案解析】由题干中的the second paragraph和选项中的direct human interference定位到第二段第二句。推理判断题。文章第二段指出，人们将热带雨林瓦解的预测和直接的人类活动联系在一起。人们认为人类活动，诸如大肆砍伐和焚烧将会造成热带雨林的瓦解，反之如果任由热带雨林自由发展，热带雨林不仅会繁茂旺盛，而且能够通过吸收过多的二氧化碳和其他温室气体拯救人类远离灾难。介绍完这一观点后，作者紧接着说“现在看来那可能只是一厢情愿的想法”，也就是说人们之前的观点是有问题的，表明作者对这一观点提出了质疑，故答案为A。

单选题 The author argues that the rising carbon levels in rain forests may ______.

A、 turn them into a major source of greenhouse gases
B、 change the weather patterns throughout the world
C、 pose a threat to wildlife
D、 ccelerate their collapse

【正确答案】 A

【答案解析】由题干中的rising carbon levels和选项中的greenhouse gases定位到第二段末句。事实细节题。文章第二段末句提到，如果热带雨林瓦解的速度显著加快，其最终每年向大气中释放35～50亿公吨的碳量，这会使森林成为温室气体的主要来源，故答案为A。

单选题 What has made it easier to turn some rain forests into farmland?______

A、 Rapid rise in carbon levels.
B、 Reckless land development.
C、 Lack of rainfall resulting from global warming.
D、 The unusual warm currents in the Pacific Ocean.

【正确答案】 C

【答案解析】由题干中的easier和turn some rain forests into farmland定位到第四段第二句。推理判断题。文章第四段提出，由于气温升高，树木需要更多的水，但是持久的干旱会使树木丧失水分。在这种恶劣的情况下，树木很容易干枯，整个森林也随之瓦解，成为农场。由此可知，全球变暖会造成干旱缺雨的后果，树木会因此干枯，最终使热带雨林轻易地变成农场，故答案为C。

单选题 What makes Brazil one of the world's top five contributors to greenhouse gases?______

A、 The domino effect triggered by the perishing rain forests.
B、 Its practice of burning forests for settlement and development.
C、 The changed patterns of winds and rains in the Amazon area.
D、 Its inability to curb the carbon emissions from industries.

【正确答案】 B

【答案解析】由题干中的Brazil和top five contributors 定位到末句。事实细节题。最后一段末句提到，在亚马逊的每个燃烧季节，拓荒者和开发者蓄意点燃的大火一年向空中排放将近5亿公吨的碳，使巴西成为导致温室气体的前五个因素之一。由此可知，为拓荒和开发进行的焚烧行为使巴西成为导致温室气体的前五个因素之一，故答案为B。